1. Properties of CO 2 gas Pure CO 2 is a colorless, odorless gas. The density is 1.98 kg/m 3 , which is heavier than air (air is 1.29 kg/m 3 ). It is 1.5 times the air.
CO 2 has three states: solid, liquid, and gaseous.
When cooled without pressure, the CO 2 changes directly from a gas to a solid, called dry ice. When the temperature rises, the dry ice sublimation directly turns into a gas. Since the moisture in the air inevitably condenses on the dry ice, the CO 2 gas generated when the dry ice is sublimated contains a large amount of water, so the solid CO 2 cannot be used for welding.
When the normal temperature CO 2 is pressurized to 5-7 MPa, it becomes a liquid. Liquid CO 2 is lighter than water at normal temperature and has a boiling point of -78 ° C.
At 0 ° C and 0.1 MPa, 1 kg of liquid CO 2 can produce 509 L of CO 2 gas.
2. Effect of CO 2 Purity on Weld Quality The purity of CO 2 gas has a great influence on the compactness and plasticity of weld metal. The main impurities in the CO 2 gas are moisture and nitrogen. Nitrogen is generally low in content and less harmful. The danger of moisture is greater. As the moisture in the CO 2 gas increases, the diffusion hydrogen content in the weld metal also increases, the plasticity of the weld metal deteriorates, pores are likely to occur, and cold cracks may occur.
According to the requirements of the CO 2 gas shielded welding process specification JB/Z286-87, the purity of the CO 2 gas for welding should not be lower than 99.5% (volume method), and the water content thereof should not exceed 0.005% (gravimetric method). In recent years, some countries require the purity of CO2 for welding to be >99.8% and the dew point below -40 °C.
3. Bottled CO 2 gas Bottled liquid CO 2 used in the industry is economical and convenient. It is stipulated that the main body of the cylinder is sprayed in silver and white, and the words "carbon dioxide" are marked with black paint.
A standard cylinder with a capacity of 40L can be filled with 25kg of liquid CO 2 , which accounts for about 80% of the cylinder volume. The remaining 20% ​​of the space is filled with CO 2 gas. The cylinder pressure gauge indicates the saturation pressure of this part of the gas. Its value is related to the ambient temperature. When the temperature is high, the saturation pressure is increased; when the temperature is lowered, the saturation pressure is lowered. At 0 ° C, the saturated gas pressure is 3.63 MPa (35.57 kgf / cm 2 ); at 20 ° C, the saturated gas pressure is 5.72 MPa (56.06 kgf / cm 2 ); at 30 ° C, the saturated gas pressure reaches 7.48 MPa (73.30) Kgf / cm 2 ); Therefore, the CO 2 cylinder should be prevented from being close to the heat source or exposed to the sun to avoid an explosion accident. When the liquid CO 2 in the cylinder is completely volatilized into a gas, the pressure in the cylinder gradually decreases.
About 0.05% by weight of water can be dissolved in the liquid CO 2 , and the excess water sinks to the bottom of the bottle. After the water and the liquid CO 2 are volatilized together, the mixed CO 2 gas is introduced into the weld zone. The water dissolved in the liquid CO 2 can also be evaporated into water vapor and mixed into the CO 2 gas, which will affect the purity of the gas. The evaporation of water vapor is related to the pressure of the gas in the cylinder. The lower the pressure in the cylinder, the higher the water vapor content.
4. Purification of CO 2 gas At present, CO 2 gas used in domestic welding is mainly a by-product of brewing plants and chemical plants, with high water content and unstable purity. To ensure the quality of the weld, the bottled gas should be treated to reduce moisture and air.
The following measures can be taken at the welding site to effectively reduce the moisture content of the CO 2 gas:
1 When replacing the new gas, first deflate for 2 to 3 minutes to eliminate the air and moisture mixed in the bottle.
2 After the gas cylinder is inverted for 1-2 hours, the valve is opened to discharge the free state water deposited underneath. According to the difference in water content in the bottle, put water once every 30 minutes, and need to release water 2 to 3 times. Then put the cylinder positive and start welding.
3 When using, install a heater in the gas path to heat the gas.
After the liquid CO 2 in the cylinder is used up, the pressure of the gas will decrease with the consumption of the gas. When the pressure in the cylinder drops to 1 MPa, the moisture contained in the CO 2 will increase by more than one time and should be stopped. If you continue to use it, there will be air holes in the weld. When welding metals that are sensitive to water. When the pressure in the bottle drops to 1.5MPa, it is not suitable for reuse.
Stainless steel doors (exterior door, entrance door)
Detailed product description
1) Material: 201 stainless steel, 304Stainless steel:
2) Standard size:2050*960mm ( the size can be customized)
3) Door leaf thickness: 70mm
4) Thickness of door leaf steel sheet: 0.7mm-1.0mm
5) Thickness of door frame steel sheet: 1.2mm-2.0mm
6) Doorsill / threshold: stainless steel
7) Design: diversified available.
8) Infillings: honeycomb paper
9) Door glass: tempered glass, transparent glass etc
10) Accessories: handles, galvanized hinges, locks, viewer, doorbell, rubber seal, installing bolts
11) Opening direction: Left or right, inward or outward
12) Opening degree: 110 degree, 180 degree.
13) Packing: PE film, plastic bag, strong carton
14) Container capacity: 90-110PCS/20Ft, 240-250PCS/40HQ (differs upon your virtual choice)
15) Delivery time: 20-25days
16) Minimum order quantity: 1* 20ft
17) Features: stainless steel door will never rust for long-term use, they are stable against the rain, sun and wind, suitable as entrance doors, exterior doors.
If you are interested in any model, please feel free to contact us for more details.
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